Among Marylandís tidal
waters,
Anabaena species and Aphanizomenonflos-aquae
are frequently found in freshwaters of the Potomac River and the upper
Chesapeake Bay. Their greatest abundances are usually observed during the
summer. These are filamentous
cyanobacteria, capable of nitrogen fixation. Anabaena is
one of four genera of bluegreen algae capable of producing neurotoxins
along with Oscillatoria, Lyngbya and Aphanizomenon.
Anabaena flos-aqua is a major producer of neurotoxins (Carmichael
1997 Advances in Botanical Research Vol

27:211-256). The best way to
minimize animal poisonings by these species that produce cyanotoxins is to
recognize you are in the area of a bloom and keep animals away from the
waters that may be toxic. No human deaths have been directly associated
with these cyanotoxins however they may cause skin irritations or nausea.

Farm animals and pets have been killed by
the toxins when the animals ingested waters containing toxic blooms of one
or a combination of these algal species. Such poisonings typically occur
when heavy surface growths or scums of the cyanobacteria have accumulated near the shoreline and animals
have easy access to toxic levels of cells (W.W.
Carmichael).
This type of toxin has been shown to persist in water for a week or more
after the bloom has disappeared.Not
all cyanobacteria blooms are toxic, and even blooms caused by known toxin
producers may not produce toxins or may produce toxins at undetectable
levels. It is not know what triggers toxin production. Recent studies have
shown the probability that an individual bloom containing Anabaena,
Microcystis, and/or Aphanizomenon will be toxic could be
between 45 and 75% (Toxic Cyanobacteria Blooms; A Field/Laboratory Guide,
Dr. M. A. Crayton). The presence of Anabaena in a water body can contribute to poor
water quality because it can impart noxious odors and disagreeable tastes
to the water.